1. Field of the Invention
This invention deals with time-delay circuits utilized for beamforming in a phased array antenna system and more particularly to a phased array antenna system utilizing switched time-delay circuits to significantly reduce the complexity of time-delay beam steering.
2. Description of the Related Art
Basically, the phased-array antenna is composed of a group of individual radiators which are distributed and oriented in a linear or two-dimensional spatial configuration. The amplitude and phased excitations of each radiator can be individually controlled to form a radiated beam. The position of the beam in space is controlled electronically by adjusting the phase of the excitation signals at the individual radiators. Hence, beam scanning is accomplished with the antenna aperture remaining fixed in space without the involvement of mechanical motion in the scanning process. An electronically steered antenna array radar is able to track a large number of targets and illuminate some of these targets with radio-frequency energy. The antenna beamwidth may be changed electronically by means of phase spoiling to search certain areas more rapidly but with less gain. Frequency agility can be achieved through changing the frequency of transmission at will from pulse to pulse, but requires sequential phase adjustments since the beam pointing direction with phase control is narrow band and changes with frequency.
Phase change at the elements due to change in frequency is exploited in frequency scanned arrays, but with phased arrays it restricts the use of wide instantaneous bandwidth, which is needed to enhance radar capabilities and performance. The narrow bandwidth of phased arrays is due to phase being controlled for the antenna aperture excitation, and steered beams will scan towards broadside as the frequency is increased, and thus move off the target.